Impedance of Alpine Hu's
05-03-2004, 10:09 PM
#22
Guest
Posts: n/a
I tested a 7894 a few years back and it did 6.2V p-p or about 2.19Vrms
The F#1 Status produced 4.56V at 196.7Ohms with a 0dB track. I was unable to clip the signal. I turned the bass up on the deck and measured just over 8V, still unclipped.
I have an IVA-D300 on the bench and will be testing it in a few weeks. They rate it at 2V on the regular outputs and 4V on the subwoofer. So we'll see what it can produce.
As for how it's measured. I typically use a 0dB track and increase the output intull I get about 1% distortion, then measure the RMS output voltage. I usually do the measurement at 1kHz, unless the effect of a filter requires a lower frequency to be used, in that case I commonly choose 60Hz.
If I am unable to get the deck to clip, I will state the 0dB level, then use internal equalization to further increase the signal into clipping and state that output level.
To acheive the 1% distortion level, I have a custom-made CD that has waveforms at many levels, decreasing in minute steps from track to track. I start at 0dB and induce clipping, then step ahead in tracks and down in level to acheive 1% distortion.
I have my 'own' formula for measuring output impedance using a small network I devised myself. It's annoying to use, but functions well.
I'd be happy to measure an Alpine deck if someone wants to drop one off with a $20 bill.. Oh, and you can chose which of the two items you get back...
The F#1 Status produced 4.56V at 196.7Ohms with a 0dB track. I was unable to clip the signal. I turned the bass up on the deck and measured just over 8V, still unclipped.
I have an IVA-D300 on the bench and will be testing it in a few weeks. They rate it at 2V on the regular outputs and 4V on the subwoofer. So we'll see what it can produce.
As for how it's measured. I typically use a 0dB track and increase the output intull I get about 1% distortion, then measure the RMS output voltage. I usually do the measurement at 1kHz, unless the effect of a filter requires a lower frequency to be used, in that case I commonly choose 60Hz.
If I am unable to get the deck to clip, I will state the 0dB level, then use internal equalization to further increase the signal into clipping and state that output level.
To acheive the 1% distortion level, I have a custom-made CD that has waveforms at many levels, decreasing in minute steps from track to track. I start at 0dB and induce clipping, then step ahead in tracks and down in level to acheive 1% distortion.
I have my 'own' formula for measuring output impedance using a small network I devised myself. It's annoying to use, but functions well.
I'd be happy to measure an Alpine deck if someone wants to drop one off with a $20 bill.. Oh, and you can chose which of the two items you get back...
05-03-2004, 11:12 PM
#23
Originally posted by Dave_MacKinnon:
I tested a 7894 a few years back and it did 6.2V p-p or about 2.19Vrms
I'd be happy to measure an Alpine deck if someone wants to drop one off with a $20 bill.. Oh, and you can chose which of the two items you get back...
I tested a 7894 a few years back and it did 6.2V p-p or about 2.19Vrms
I'd be happy to measure an Alpine deck if someone wants to drop one off with a $20 bill.. Oh, and you can chose which of the two items you get back...
05-11-2004, 06:37 AM
#27
0 Watt CAFz'r
Join Date: May 2004
Posts: 8
Hi all.
Alpine stopped putting output impedance in their owners manuals and tech docs over 6 years ago because the spec started to become a very misunderstood number. The rating that is currently in the Manual is as follows
Preout Voltage: 4V @ 10Kohms
The 10Kohms is refering to the input load that an amp is providing. So, if that deck is connected to an input of an amp that is 10Kohm the deck will produce 4V of preout voltage. The higher the input impedance of a given amp, the lower the preout voltage will be from these headunits and visa-versa. Output impedance became a marketing tool decades ago in home audio, because, the output voltage is a standard 0.5V. In this case a lower output impedance can create more power out of a particular source. Unfortunatly this trend has become a marketing tool in car audio, where output voltage has been very high for years (higher voltage is a better way to lower noise floor in the nasty automotive environment). Combine a 4 or 5 volt output with ultra low output impedance (below 150 ohms)and a tremendous amount of power is created in the preamp signal. This is a good thing if the source can do this cleanly (harder and harder with today's feature packed head units),but it requires a comlpex and expensive input stage. I know a few maunfactures that use 22Kohm + inputs with large preamp buffering devices. These amps are only compatible with outputs that are below 60 ohms @ 4 or 5 volts, otherwise they don't produce what they should for power. So, the output and input impedances need to form a relationship. Is there any benefit to going to such extremes, other than forcing the consumer to stay with one brand? The reviews are mixed; some say that low output impedance heads aren't as open in the midrange but the bottom end is more robust, while others say the increased power is effective across the entire audio spectrum. The truth is that there is not enough empirical evidence to show a definite improvement (over a 4 or 5 volt clean output at 200-300ohms with a 10K input). The main issue here is that ultra low output impedance will very easily saturate most amps on the market,(10Kohms is a widely accepted standard)assuming the now common 4-5 volt range is used. All Alpine sources use a 300 ohm output and all Alpine amps and processors use a 10Kohm input. The preout stages are very clean "all the way to 35" assuming the amp has at least a 10Kohm input. In a nutshell, they work great together and with a multitude of other brands. [img]smile.gif[/img]
Alpine stopped putting output impedance in their owners manuals and tech docs over 6 years ago because the spec started to become a very misunderstood number. The rating that is currently in the Manual is as follows
Preout Voltage: 4V @ 10Kohms
The 10Kohms is refering to the input load that an amp is providing. So, if that deck is connected to an input of an amp that is 10Kohm the deck will produce 4V of preout voltage. The higher the input impedance of a given amp, the lower the preout voltage will be from these headunits and visa-versa. Output impedance became a marketing tool decades ago in home audio, because, the output voltage is a standard 0.5V. In this case a lower output impedance can create more power out of a particular source. Unfortunatly this trend has become a marketing tool in car audio, where output voltage has been very high for years (higher voltage is a better way to lower noise floor in the nasty automotive environment). Combine a 4 or 5 volt output with ultra low output impedance (below 150 ohms)and a tremendous amount of power is created in the preamp signal. This is a good thing if the source can do this cleanly (harder and harder with today's feature packed head units),but it requires a comlpex and expensive input stage. I know a few maunfactures that use 22Kohm + inputs with large preamp buffering devices. These amps are only compatible with outputs that are below 60 ohms @ 4 or 5 volts, otherwise they don't produce what they should for power. So, the output and input impedances need to form a relationship. Is there any benefit to going to such extremes, other than forcing the consumer to stay with one brand? The reviews are mixed; some say that low output impedance heads aren't as open in the midrange but the bottom end is more robust, while others say the increased power is effective across the entire audio spectrum. The truth is that there is not enough empirical evidence to show a definite improvement (over a 4 or 5 volt clean output at 200-300ohms with a 10K input). The main issue here is that ultra low output impedance will very easily saturate most amps on the market,(10Kohms is a widely accepted standard)assuming the now common 4-5 volt range is used. All Alpine sources use a 300 ohm output and all Alpine amps and processors use a 10Kohm input. The preout stages are very clean "all the way to 35" assuming the amp has at least a 10Kohm input. In a nutshell, they work great together and with a multitude of other brands. [img]smile.gif[/img]
